An investigation of the role of axonal transport of membrane and protein in the steady state maintenance of synaptic function. Using enzyme cytochemical techniques we are analyzing the transport function of axonal smooth endoplasmic reticulum in cultured neurons. Specifically we are interested in the mechanism by which anteriorgrade and retrograde transport of membrane and protein may be segregated, in the role of axonal microtubules in retrograde transport and in the effects of inhibition of oxidative metabolism on transport and on fusions between membrane-delimited axonal compartments. In addition, we are studying acetylcholine induced stimulation of endocytotic activity as sympathetic terminals and the relative roles of synaptic vesicle membrane reuse and turnover at these terminals. We are also evaluating the relative importance of new synaptic vesicle formation from the axonal smooth endoplasmic reticulum, using an electron dense catecholamine, 5 OH dopamine. Our studies also include an evaluation of the localization and axonal transport of acid hydrolase and their possible role in intraaxonal membrane turnover. BIBLIOGRAPHIC REFERENCES: Teichberg, S. and D. Bloom: 1976. Uptake and Fate of Horseradish Peroxidase in Axons and Terminals of Sympathetic Neurons. J. Cell Biol. 70: 285a. Teichberg, S. and D. Bloom: 1977. Acetylcholine-enhanced Endocytosis at Terminals of Cultured Sympathetic Neurons. Fed. Proc. 36: 599.